Problematic Messaging System

I received a notice saying I got a letter from a given player, but the lefthand pane is empty, and all I can seem to do is delete the notice. My inventory does not contain any letter-like objects… that don’t count as plot items. What am I missing here?

I’m pretty sure letters end up as messages in the righthand pane, since they shouldn’t need to be accepted. Though I suppose if someone accidentally sent an empty letter it might look like a notice that they sent you a letter and nothing more?